1. Field of the Invention
The invention relates to electronic packaging, and particularly to a low temperature right angle chip connection technique.
2. Description of the Prior Art
Low temperature packaging techniques generally involve the use of materials having similar coefficients of expansion, with contacts which survive temperature cycling and still provide electrical contact at low temperatures.
The very low temperatures (4.2.degree. K.) used with Josephson junction circuits are subject to special problems and advantages. The advantages are related to the superconducting nature of the circuitry, and, even where the circuitry is not superconducting, the excellent heat transfer ability of the liquid helium which is the source of the low temperatures. Special problems are related to the expansions and contractions of repeated cycling between room temperature and liquid helium temperature, particularly where joints having mating materials of different thermal expansion coefficients are present.
Furthermore, in order to take advantage of the high speeds and other virtues of Josephson junction technology, it is necessary to make the wire lengths short so as to eliminate the time loss of signal propagation even at its near-speed-of-light velocities through the conductors. Short conductor lengths tend to require three dimensional packaging. Such packaging requires right-angle connections in addition to those connections normally required by a two-dimensional package. Right angle connections are made in a linear configuration, at the intersection of two planes, between conductors located in a horizontal plane and conductors located in a vertical plane. Right angle connectors provide connection for horizontal conductors to vertical conductors.
High circuit densities lead to a requirement for a high density of right angle connections in such a package. These connectors typically require solder or microplug structures for mechanical and electrical bonding of mating conductors. The processes required by such structures have tolerances far exceeding lithographic tolerances.
The linear density of connectors is not lithographically determined; the connector pads are bigger than the conductor lines which they connect.
Right angle connectors closely spaced in a linear array can present a relatively high inductance which results in unacceptable crosstalk unless signal shaping or other performance reducing measuring are taken.
The striplines and the right angle connection may be molded as two transmission lines of a particular characteristic impedance, separated by the connector modeled as a relatively large inductive discontinuity between them.